1. Field of the Invention
This invention relates to a developing apparatus preferably for use in an image forming apparatus such as an electrophotographic copier, an electrophotographic printer, a facsimile apparatus or a word processor, or a process cartridge.
2. Related Background Art
In an electrophotographic copier or the like, a latent image formed on an electrophotographic photosensitive drum which is an image bearing member is developed into a visible image with a toner, and a developing apparatus for supplying the toner to the photosensitive drum is comprised of a developing frame containing the toner therein, and a developing roller which is a developer carrying member and a developing blade which is a developer regulating member mounted on the developing frame. The toner is fine powder, and as shown in FIG. 8 of the accompanying drawings, in order to prevent the toner from leaking through the gaps between the developing frame 50 and the developing roller 51, elastic members 52 such as felt or rubber for sealing the gaps between the developing frame 50 and the developing roller 51 in the lengthwisely opposite end portions of the developing roller 51 have been attached.
If the toner used is a magnetic toner having magnetism, instead of the elastic members 52, as shown in FIG. 9 of the accompanying drawings, magnetic seal members 53 each having an arcuate portion 53a opposed to the developing roller and formed of a magnetic material are mounted so as to provide a minute interval with respect to the developing roller, and the magnetic toner is attracted by a magnetic force to thereby prevent the leakage of the toner. These magnetic seal members 53 do not abut against the developing roller 51 and therefore, there is the advantage that it becomes possible to make the rotational torque of the developing roller 51 small and the assemblage of the magnetic seal members to the developing frame 50 becomes easy.
Also, in the developing apparatus, a developing blade for regulating the layer thickness of the toner borne on the developing roller 51 is mounted on the developing frame 50, and in order that the toner may not leak from the gap between this developing blade and the developing frame 50, as shown in FIGS. 9 and 10 of the accompanying drawings, a lower blade seal member 54 is mounted between the developing frame 50 and the developing blade (not shown). In a construction in which the gaps are sealed by the magnetic seal members 53, the lengthwise end portions of this lower blade seal member 54 and the magnetic seal members 53 are mounted with minute spacings h and i therebetween, and blade end portion seals 55 are mounted to prevent the toner from leaking through the minute gaps h and i when the developing blade is mounted.
The magnetic seal members 53 are such that only the arcuate portions 53a thereof opposed to the developing roller 51 are formed of a magnetic material and the straight portions 53b thereof opposed to the blade end portion seal members 55 and the lengthwise end portions of the lower blade seal member 54 have no magnetism. Therefore, to reliably prevent the leakage of the toner, it is necessary to enhance the dimensional accuracy of the minute spacings h and i.
The magnetic seal members 53, however, are rigid members and the developing frame 50 on which they are mounted is also a rigid member and therefore, mounting backlash is liable to occur. Therefore, it has been necessary to effect the mounting of the seal members 53 especially carefully.
It is an object of the present invention to provide a developing apparatus in which the leakage of a developer is prevented without the mounting accuracy of magnetic seal members being enhanced.
It is another object of the present invention to
Further, in order to prevent the toner from leaking from between the developing blade 9d which is a developer regulating member and the developing frame 12 when the developing blade 9d is mounted, as shown in FIGS. 4 and 5, a lower blade seal member 16 of urethane or like material is stuck on the developing blade mounting position of the developing frame 12 with substantially the same length as the length of the developing blade 9d, and the developing blade 9d is mounted thereon. The magnetic seal members 14 are mounted so that the straight portions 14b thereof may be opposed with minute gaps h and i from the lengthwise end portions of the lower blade seal member 16. Also, blade end portion seal members 17 are mounted to prevent the toner from leaking from the minute spacings h and i when the developing blade 9d is mounted.
The straight portions 14b of the magnetic seal members 14 are mounted so as to be opposed to the lengthwise end portions of the lower blade seal member 16 and the blade end portion seal members 17 with the minute gaps h and i. The magnetic seal members 14 have magnetic portions formed not only on the arcuate portions 14a but also on the straight portions 14b and therefore, a magnetic force acts also on the gaps h and i. Therefore, the magnetic toner in the gaps h and i is attracted by the aforementioned magnetic force and it never happens that the toner leaks from the gaps h provide a developing apparatus in which the developer leakage preventing effect of magnetic seal members is extended to the vicinity of a regulating member.
Further objects and features of the present invention will become more fully apparent from the following detailed description when read with reference to the accompanying drawings.